Fuel Filler Corrosion

[petestoy]

I have a 2006 LBZ which i purchased about a mnth ago, their is corrosion around the inside of the Fuel filler neck where the cap screws in and on the cap? This has to be the first vehicle that i have seen it on. I have heard of some honda's maybe toyota's that had a similiar issue and it was a venting issue? Any ideas would be appreciated.

[LittleBigRig]

The filler neck on on my 2001 (it has 107,000 miles on it today) was corrosion-free up until about the time that they reformulated the diesel fuel for the 2007 model years. I'm not a chemist, but I would say that there is something in the new formula that is causing the corrosion.

I haven't noticed anything unusual in the fuel filter at the regular 15k replacement intervals, but I am keeping my eyes on it closely. Up to this point, the corrosion appears to be the garden variety grey oxidization that you can get on aluminum. While it isn't flaking or anything, if you wipe your finger across it it will rub off on your finger.

On a similar note, there are some issues over at Ford with corrosion on the inside of the fuel tanks of Superdutys, and in fact, it is so bad in some cases that the inside of the tanks are delaminating and beginning to cause downstream fuel filter and injector problems. They are blaming biodiesel as the cause, but I can tell you that the diesel that goes in my rig has never been anything but straight-up dino variety, so I know that at least in my case, biodiesel is not causing my problem.

[LittleBigRig]

I took a closer look at fill-up today and saw some significant changes in the filler tube - not only did I see the aluminum oxidation as previously reported, but now it has progressed to old-fashioned rust.

This is a southern truck that has never seen a salty road, has never had any wierd fuel except the standard dino-type, is driven every day, has been meticulously maintained, and is always filled to full at the pump.

Is no one else seeing this?

[mattb5150]

When I bought my 2003 used about a year and a half ago the filler neck was rusted and I replaced it. The original owner was from southern California, no salt. I've seen older cars where the owner lived at the beach rusting through the body where salt spray is the culprit but on the filler neck I would think this would not be probable.

[LittleBigRig]

Update from my earlier post. In May of 2009 (this year), I replaced the fuel filler neck in my truck with a brand new one from GM. Afterwards, I was careful to run only Shell diesel and no additives. By July 2009 (about two months later), I noticed the same gray discoloration that I had seen on the original filler neck and now we are heading toward the same good old rust that was on the original one.

Is anyone seeing any issues like this in the older Duramaxs? I run nothing but the best diesel, no additives, change the fuel filter more often than recommended, and drive the truck daily. It now has 120,000 miles on it and I am looking at buying a new truck. I would love to have another diesel, but unless I can figure out what is causing this problem, I'm reluctant.

Btw, the truck has been in North Georgia the whole time (no trips to the beach) since the filler neck was replaced. So that isn't a factor. I don't have a clue what could be causing it. Any ideas?